Stability of cemented in-line pegged glenoid compared with keeled glenoid components in total shoulder arthroplasty

Considerable interest has been focused on the design of the glenoid component used in total shoulder arthroplasty in order to reduce the risk of loosening. One design-related feature that has attracted attention is whether to use pegged or keeled cemented glenoid components. The main purpose of this study was to compare the fixation of cemented keeled glenoid components with that of cemented in-line pegged glenoid components.

In a prospective randomized study, we compared the stability of cemented, all-polyethylene, keeled glenoid components and cemented, all-polyethylene, in-line three-pegged glenoid components by radiostereometric analysis. Twenty-seven shoulders in twenty-five patients with osteoarthritis (twenty-two shoulders had primary and five shoulders had secondary osteoarthritis) were included. There were sixteen women and nine men, and the mean age was sixty-four years. Radiostereometric analysis and conventional radiographs were carried out at five days, at four months, and at one and two years postoperatively.

The mean Constant and Murley score preoperatively and two years postoperatively was 25 and 70, respectively, for shoulders with the keeled glenoid component and 22 and 70 for the shoulders with a pegged component. No significant difference was detected between groups with regard to the average micromigration of the glenoid components at any of the time points. The average translation was <1 mm, while the median value was <0.3 mm at two years, with no significant difference between the different axes. In five shoulders (three with the keeled component and two with the pegged component), translation at two years was >1 mm. In fourteen shoulders (eight with the keeled and six with the pegged component), the rotation around one or several axes was >2 degrees . We were not able to detect any specific pattern with regard to movement for either type of component nor were we able to detect any difference between the two types of components in the way they migrated, if migration occurred.

Cemented all-polyethylene keeled or in-line three-pegged glenoid components appear to have similar stability during the first two years after surgery. Studies with a longer follow-up period are needed to relate these findings to long-term clinical and radiographic outcomes.